The invention provides a voltage balancing system for balancing controlling of voltage of battery cells including a first set of battery cells and a second set of battery cells connected in series. The system includes a high-side analog front end (AFE) connected to the first set of battery cells, a low-side analog front end (AFE) connected to the second set of battery cells, a microcontroller communicating with the high-side AFE and the low-side AFE, and a communication isolating module interconnecting between the high-side AFE and the microcontroller. The system further includes a balancing module arranged at a back end of the low-side AFE or the high-side AFE to equalize voltages output by the low-side AFE and the high-side AFE. Compared with the prior arts, the system employs a balancing module to balance the voltages of the two sets of battery cells, which can shorten the voltage difference therebetween.